New to Airheads [Archive]

miltown

09-16-2007, 09:56 AM

Hey just purchased a 83 R80RT with 23K on it. First BMW and I love the ride. I was wondering are these Airheads suppose to be so vibrationish. It seems to vibrate at slow speeds .At high speeds it's smooth as glass. The idle is up at about 1100rpm. I think that is normal for the bike. I'm not familar with these bikes so I don't know. I was told that they are a little on the rough side.

paul

lkchris

09-16-2007, 10:10 AM

R80RT should be smooth as glass at all speeds.

Don't lug it, though, as this will cause some vibration.

Clearly when the engine gains revs it has to operate the same on both cylinders. Carburetor misbalance can cause uneven running and some vibration. Of course, first, valves must be equally adjusted, too.

Your best bet is to find a fellow Airhead owner via your local BMW club and compare notes and possibly lean how carbs are adjusted and balanced.

miltown

09-16-2007, 11:31 AM

Not sure what "lug it" means. Valves have been adjusted. Carbs were adjusted and cleaned also. Still the same as when I bought it. Any MOA'esr out there in Milwaukee? The carbs were not balanced though. Also going through the seat issue. Any suggestions?

paul
'83 R80RT

Boxerkuh

09-16-2007, 12:00 PM

Welcome to the Airhead family. Lugging it means that you are riding around in very low RPM's in too high of a gear. The airheads don't mind being reved around. With a stock electrical set up, your alternator will not begin re-charging the battery until around 3000 rpm's; therefore it is good if you at least keep the engine at that engine speed. If you have an upgraded 400 watt alternator kit in it, the alternator will begin re-charging the battery around 2000 rpm's. Hope that helps you a little bit. My food for thought anyway...:eat :drink :blush
What do you mean by seat issue? :ear :lurk

DennisDarrow

09-16-2007, 12:35 PM

Welcome aboard Paul. There is an abundance of info on carb syncing etc here and in the technical articles at Airheads Beemer Club............

BMW's are NOT rough.........especially the lower CC versions.............keep it above 3000 RPM when just cruisin along with the sweet spot usually around 4000 or so.....NOTHING wrong with 5000 all day long..................

What are your former rides?.............wondering if a bit on the cushy side?.........70s and 80s BMW's were competing against the Brit bikes and were set up accordingly........the "Touring" on a lead sled versions came to being in the 90's...........the seats accordingly are made to "move around on"..........anyway....just my opinions................

RIDE it Paul...............Dennis

miltown

09-16-2007, 01:44 PM

Thanks for all the replies! I thought that was what "lug it " meant but wanted to confirm. Never assume. I have pretty much been a honda rider. All CB750's had a kawasaki kz650. Wanted more of a "Touring" bike. Was going to get a Concours but then this bike came along and I really liked it. Thanks for the welcome and advice Dennis. Boxerkuh the stock seat is very uncomforatable on longer rides. I have riden the bike on two 3 hr rides and my back was shot after each one. I hear the hems and haws on Corbins. Maybe an Airhawk. Or new foam for the seat. I'm open.

paul

mikegates

09-16-2007, 04:21 PM

not milwaukee, but Eagle there is a few of us around

benway

09-16-2007, 06:27 PM

"It seems to vibrate at slow speeds "

do you mean engine-- rpm or speed-- mph?

does the vibration go away if you pull the clutch in, or coast in neutral?

as you have no vibe at higher speed, it might be your idle balance is off.

check that all carb body holes etc are clear. and try and balance at idle

also check snowbums and duane aushermans sites for good info

hope that helps

osbornk

09-16-2007, 08:52 PM

Vibration is relative. The vibration you speak of is due to the twin cylinders and low rpms. The UJMs you are used to have less vibration but are more buzzy. Top me, the buzziness caused numbness of my hands in the 750 Hondas and 550 Kawasaki I had as well as the K100RT BMW. The 700cc Honda Magna I had was smooth as silk at any speed. I went from them to a silky smooth BMW K75RT and then to my current R80RT and R1200CLC. I think the twin cylinder BMW have more personality than the others and plan on keeping them both but I miss the Magna.

26667

09-16-2007, 08:54 PM

Reg Pridmore says they used to run the airhead motors at redline "all day" on the bench at the factory. it's built to go fast. The 1000 cc versions have a 'sweet spot' from about 4200 depending on a variety of factors; cams, final drive ratios, etc. but run it fast. don't short-shift it. if it's not smooth at idle, learn how to synch and balance the carbs and adjust the valves. you'll be a much happier airhead owner. and ditto on snowbum's site, clymer or haynes manuals, finding your local airheads chapter(see their website and JOIN). There are some very savvy cheeseheads running airheads.
and welcome. keep us posted, and see you down the road!:bolt

26667

09-16-2007, 09:04 PM

also check the flea market "accessories" section somebody's got lots of back issues of "moa news". free. more than a bargain as a resource. plus it'll help get you thru the long westconsin winter coming soon to a driveway near you.

535is

09-17-2007, 02:47 PM

Vibration is relative. The vibration you speak of is due to the twin cylinders and low rpms.

+1 With your old fours, you never felt the individual cylinders firing, except possibly at a slow idle. A twin has a completely different feel. A V-twin (especially a single pin crank V-twin) will always have uneven firing pulses, just closer together. It also has an uneven vibration from the piston masses moving together instead of in opposition. Where the BMW is distinct from other twins is at higher speeds. The BMW's boxer crank design smooths out at higher speeds because the firing pulses are even and because the moving mass of the piston assemblies is balanced. But at idle and at low speeds, you'll feel it firing.

sumran

09-18-2007, 10:32 AM

535is

09-18-2007, 10:50 AM

I had previously owned Japanese bikes. I had heard about the smoothness of BMW's and had very high expectations in that regard. The bike is everything I expected in the right RPM range, but has a bit more of a lope at idle than I expected. Now that I understand the design and behavior of the bike better, I have come to appreciate it as part of the airhead personality. My expectations weren't based on bad information, just incomplete information.

Yup. I heard the story of a guy with his Gold Wing in for service at the Honda shop who took a demo ride on a Pacific Coast. When he got back, he said it felt great in every way except it seemed to be missing on one or two cylinders. :brow

The punchline is, the PC is an 800cc V-twin. :D

miltown

09-22-2007, 12:09 AM

I had read some tech articles on balancing the carbs so I had decieded to give it a go. I did the first step and rechecked all my adjustments. Took it out for a ride. That had did it. My suspect was the throttle cables. I synced them again for play and response so that they both worked as exact as I could get it. Simple. So I think I'll wait on the balance. Yeah that snowbum is intense , his article is what I read and I felt pretty confident with the info to balance the carbs. With that out of the way I now have a rear drum issue with gear fluid seeping out of the brake cam. Nothing seems worn. I'm going to replace the o-rings ,but I think I just added to much gear lube. It says 350 cc in the clymer manual. Is that accurate ? They also say 250 cc for '70 to '80 and 260 cc for R1000GS. The 350cc is for all others. I think that is what I fall under. I have to say in the short time I have owned this bike and joined this club ( at the previous owners advice) I'm amazed at the response. I enjoy wrenching on this bike and I appreciate the help.Thanks all.

paul .
'83 R80RT
'73 Honda CB750
'73 Honda CB350 (but it might be sold)

miltown

09-22-2007, 12:16 AM

Just wanted to add I agree with you sumran and 535is. I also think it is a beautiful thing to. A very unique feel. Sometimes I head up towards St. Nazains by Manitowoc . I'll have to email you 535is if I head up that way.

paul

20774

09-22-2007, 09:46 AM

Yup, 350cc in the rear bevel drive for 1981 on...

DennisDarrow

09-22-2007, 10:44 AM

Actually YOU have sycnd and balanced the carbs if you got the cables right.........yes, you still possibly need to get the idle correct on each carb; but that has little to do with actual vibrations at cruising RPM..........

You might want to put different topics into a NEW thread..........that said.......most folks dont measure how much 90 weight to put into the final drive.......fill to the bottom of the threads at the rear end/differential fluid input/checking plug............Or if you are talking about the driveshaft 2mm of fluid above the driveshaft is adequate..............measure this at the input plug on the driveshaft with a straight piece of rod (big paper clip) going straight down through the threaded input hole......................Dennis

miltown

09-22-2007, 11:32 AM

Thanks guys. I was just wondering on the fluid fill because of the fluid seepage through the brake cam. I'll replace the o-rings and see what happens. I'll get a hang of this posting thing.

paul

20774

09-22-2007, 12:04 PM

most folks dont measure how much 90 weight to put into the final drive.......fill to the bottom of the threads at the rear end/differential fluid input/checking plug............Or if you are talking about the driveshaft 2mm of fluid above the driveshaft is adequate..............measure this at the input plug on the driveshaft with a straight piece of rod (big paper clip) going straight down through the threaded input hole

On my /7, I've never found this easy or possible to do. For this, I usually go with the correct volume which can be anywhere from 50cc to 150cc. As long as there's some, you're probably OK.

Isn't the rear drive fill hole on the '83 or some later bikes actually the breather vent? I think in those case, you can't see the bottom of the threads, because you're filling at a different location. I might have the year/model wrong, but at some point, you really do have to go with the volume.

miltown

09-22-2007, 12:34 PM

Yeah I'm going with volume. My real problem is why is gear lube seeping out of the brake cam and getting all over my brake shoes. It's a slow leak but by day 3 I have no rear brakes. The level of the fluid is right up to the point were the brake cam goes through the finial drive. The level check screw is also at that point on the back of the finial drive. When I unsrew the level check I see the brake cam and some fluid. When i pull out the brake cam the fluid is right at that level. So technically it is were it is suppose to be. I'm having a hard time locating metic 0-rings size 10x2. And I also can't understand why the o-rings would just fail. Maybe bad bushings but they look ok visually.

paul

PHMarvin

09-22-2007, 04:29 PM

Hi, Paul,
I have the genuine BMW repair manual for the R100 bikes (same final drive as the R80 for the same year, only difference is the ratio). The specification is .35 litre (350cc) for '81-'84 airheads. I hope this helps.

kstoo

09-22-2007, 06:24 PM

Any MOA'esr out there in Milwaukee?

The carbs were not balanced though.

not Milwaukee, Burlington is close though.

I just bought a carb synch tool after always balancing carbs by ear. I can feel the difference. Subtle but smoother.

GlobalRider

09-22-2007, 06:35 PM

I'm not familar with these bikes so I don't know. I was told that they are a little on the rough side.

paul

At and off idle, don't expect them to be as smooth as an in-line four.

Have another rider in your area that knows these bikes ride it and comment.

Welcome to the best series of BMW motorcycle engines made. ;)

97077

09-22-2007, 08:42 PM

I have 3 r80's and by far my seat of choice is my Russell Daylong. My 2 Corbins ( solo gunfighter and a two up) I would trade for a Russell in a second. Welcome to the Air Heads and BMW.

535is

09-26-2007, 12:48 PM